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| A B C D E F G H I J K L M N O P Q R S T U V W X Y Z # |
Factor VIII Activity, Clotting
Test Code10150
CPT Codes
85240<br>Limited Access Code
Preferred Specimen
1 mL platelet-poor-plasma collected in a 3.2% sodium citrate (light blue-top) tube
Minimum Volume
0.5 mL
Instructions
Platelet-poor plasma: Centrifuge light blue-top tube for 15 minutes at approximately 1500 g within 60 minutes of collection. Using a plastic pipette, remove plasma, taking care to avoid the WBC/platelet buffy layer and place into a plastic vial. Centrifuge a second time and transfer platelet-poor plasma into a new plastic vial. Plasma must be free of platelets (<10,000/mcL).
Freeze immediately and ship on dry ice.
Note: Storage of whole blood at refrigerated temperatures prior to processing may lead to cryoprecipitate formation and falsely low Factor VIII and von Willebrand Factor studies.
Freeze immediately and ship on dry ice.
Note: Storage of whole blood at refrigerated temperatures prior to processing may lead to cryoprecipitate formation and falsely low Factor VIII and von Willebrand Factor studies.
Transport Temperature
Frozen
Specimen Stability
Room temperature: Unacceptable
Refrigerated: Unacceptable
Frozen: 30 days
Refrigerated: Unacceptable
Frozen: 30 days
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Hemolysis • Received thawed
Methodology
Clot Detection
Setup Schedule
Set up: Mon-Fri; Report available: Next day
Reference Range
50-180 % normal
Clinical Significance
This test is useful to evaluate a prolonged aPTT, and for the evaluation of Hemophilia A and von Willebrand Disease. The most common form of hemophilia is caused by a deficiency of Factor VIII. Hemophilia A is an X-linked disorder affecting between 1 in 5,000 to 10,000 males and results in decreased levels. Borderline low factor VIII activity can be seen in female carriers of the defective factor VIII gene. The presence of factor VIII antibodies (autoantibodies or antibodies resulting from replacement therapy) can result in low factor VIII levels. Typically this test is combined with other screening tests (eg. von Willebrand factor, Ristocetin Cofactor Activity) to evaluate for the presence von Willebrand disease. Factor VIII is a positive acute phase reactant and levels will increase in a variety of clinical scenarios.
Anticoagulant interference: Expected impact by therapeutic levels (potential interference depends upon drug concentration): Warfarin: no effect; Heparin (UFH or LMWH): no effect to inhibitor pattern; direct Xa (eg Apixaban, Edoxaban, Rivaroxaban) or thrombin inhibitor (eg. Dabigatran, Argatroban) therapy may cause falsely low FVIII activity levels (avoid for approximately 2-3 days before testing if not clinically contraindicated).
Other limitations: Factor VIII levels may be falsely low due to Lupus anticoagulant and other factor specific inhibitors (eg. factor IX, XI, XII) and therefore a chromogenic Factor VIII activity assay using bovine reagents is suggested (test code 16049).
This test is NOT recommended for patients receiving emicizumab (ie. Hemilbra) as this therapy will yield falsely elevated values.
Anticoagulant interference: Expected impact by therapeutic levels (potential interference depends upon drug concentration): Warfarin: no effect; Heparin (UFH or LMWH): no effect to inhibitor pattern; direct Xa (eg Apixaban, Edoxaban, Rivaroxaban) or thrombin inhibitor (eg. Dabigatran, Argatroban) therapy may cause falsely low FVIII activity levels (avoid for approximately 2-3 days before testing if not clinically contraindicated).
Other limitations: Factor VIII levels may be falsely low due to Lupus anticoagulant and other factor specific inhibitors (eg. factor IX, XI, XII) and therefore a chromogenic Factor VIII activity assay using bovine reagents is suggested (test code 16049).
This test is NOT recommended for patients receiving emicizumab (ie. Hemilbra) as this therapy will yield falsely elevated values.
